fix: honor explicit format_d3 in tooltips and big numbers

[nishantmonu51]

• Measures with an explicit format_d3 were humanized in the tooltip and big-number formatter contexts, capping precision at ~2 decimals. Sub-cent measures like $0.0002 with format_d3: "$,.4f" rendered as ~$0.00 on the big number and in hover tooltips, while the leaderboard, TDD, and pivot showed full precision.
• createMeasureValueFormatter now honors an explicit d3 format in every context except axis (tick labels stay humanized so they remain compact). This fixes the explore big number and its hover tooltip, the canvas KPI, the leaderboard/dimension table/pivot cell tooltips, and the cell inspector in one place.
• The time-series chart hover readouts now use the tooltip formatter context instead of the table default; the measure-chart refactor (chore/feat: MeasureChart refactor #8752) predated the tooltip-context standardization in APP-768: fix: tooltip formatting for measure values across leaderboard, dimension table, and pivot table #9109. This also removes the remaining ~$0.00 path for sub-cent hovers on format_preset measures.
• format_preset measures keep their humanized big numbers. Updated the unit specs and the e2e expectation for the d3-formatted measure, and fixed the docs paragraph that described the old big number behavior.

Checklist:

• Covered by tests
• Ran it and it works as intended
• Reviewed the diff before requesting a review
• Checked for unhandled edge cases
• Linked the issues it closes
• Checked if the docs need to be updated. If so, create a separate Linear DOCS issue
• Intend to cherry-pick into the release branch
• I'm proud of this work!